Chapter 2. Current Status of Energy in Cameroon
3.3 Summary and Implications
In this section, some key strategies and plans of Cameroon related to RE were discussed. Among the various strategies, the highly regarded Vision 2035 emphasizes RE as a significant method to establish energy infrastructure and respond to environmental problems. The INDC, which will have the same authority as domestic law once ratified, defines RE as the most effective method for reducing the emission of GHG in the country. The goals of this initiative are ambitious, including a 25% target for RE in total generation by 2035.
City 5year runoff (kW) Solar PV capacity
(kWp) RE mix (%)
Messok 18 31 50%
Somalomo 7 12 50%
Ouli 39 55 50%
Ako 81 111 50%
Furuawa 30 41 50%
Dikome 131 247 50%
Toko 7 15 50%
Idabato 25 45 50%
Total 338 557
demand of 23,730 GWh in 2035. Moreover, there is not enough room for comprehensive plans of high- potential solar and bioenergy projects. The PDER of 2016, which amended the existing PDER and the 2014 PDSEN, has not considered grid-connected RE projects, leading to major RE projects not being reflected.
This dims the prospects of RE deployment.
This gap between upper-level strategies and sub-level implementation plans is proof that the declared importance of RE in the upper-level strategies remains only an announcement. This is ascribed to RE not being prioritized in the narrower scope of the lower-level plans.
In view of the above, a separate master plan is required solely for RE (REMP). Deployment targets for RE should be formulated with newly defined its vision, policy goals and specific strategies. Moreover, REMP should include separate policy measures and programs solely customized for RE deployment to achieve the vision and the goals. In addition, the major contents of the REMP thereof must be fed back into the existing strategies and plans to enable the entire system to function flawlessly.
Additionally, the active implementation of the National Energy Efficiency Plan (PNEE), indicated in Figure 3-2, would lower the national energy demand significantly, which, in turn, would lower the RE deployment targets in terms of volume. Therefore, the PNEE must be updated to incorporate the REMP and must be implemented actively as well.
[Figure 3-2] Position of REMP with respect to other strategies and plans
PNEE: Plan National d’EfficacitéEnergétique Source: KEEI
4.1 Status of RE Technology by Source
4.1.1 Solar PV
4.1.1.1 Overview of Solar PV Power Generation
The solar PV system, a power generation technology that converts sunlight directly into electricity, consists of the solar cell module (an array of multiple modules) equivalent to a generator, the capacitor for storing electric energy, the power conditioning system (PCS) that converts the direct current from a photovoltaic array to an alternating current, the system control and monitoring, and the load.
[Figure 4-1] Solar PV power generation system and components
Source: KEA (2016), Renewable Energy White Paper
The solar cell is the critical component of the solar PV system. A photovoltaic cell is a semiconductor device that converts light into electricity. A single solar cell, which is the smallest unit of a solar panel, yields an extremely low voltage of approximately 0.5~0.6 V. Therefore, several cells are connected in series
4. Technical Characteristics of Renewable
Energy by Source
in the form of a panel (the photovoltaic module) to create additional voltages of a few volts to several tens of volts or higher. These modules are inter-connected in series-parallel with the desired loading capacity. Such a combination is called the solar array and can be considered equivalent to the generator of the rotary power-generation system. The PCS/inverter, which is a power converter, acts as a transmitter by converting the direct current generated from a solar array into an alternating current of power frequency and voltage, and subsequently connecting the resulting current to power grids. The PCS/inverter provides electrical monitoring and protection of the direct and alternating currents of the system.
[Figure 4-2] Basic structure and working mechanism of solar cell
Source: KEA (2016a), Renewable Energy White Paper
[Fig. 4-2] illustrates the basic structure of a solar cell and the production process of electricity. Solar cells can be fabricated by combining p-type and n-type semiconductors (p-n junction) and applying metal electrodes to the front and back surfaces. When light is absorbed from a semiconductor, electron-hole pair is formed, and the electrons and holes flow in opposite directions due to the electric field present around the p-n junction. As a result, electricity is generated in the external circuit connected with lead wires.
4.1.1.2 Trends in Domestic and International Technology Development
[Figure 4-3] Worldwide trend of solar cell efficiency by type
Source: NREL (2016)
❙ Table 4-1 ❙ Efficiency and characteristics of solar cells by type
Type Characteristics Conversion
efficiency Stage Major Korean and overseas corporations
Silicon based Crystalline
Mono crystalline
Using thin monocrystalline Si wafer around 180 µm thickness
Advantage: performance, reliability Challenge: potential for lower
cost
~20%
(module) Commercialization
(South Korea) Hyundai Heavy Industries, LG Electronics,
Shinsung Solar Energy (Overseas) Sunpower (US), Sharp, Panasonic, Mitsubishi
Electric (Japan)
Polycrystalline
Using polycrystalline wafer consisting of small crystals
Advantage: cheaper than monocrystalline wafer Challenge: less efficient than
monocrystalline wafer
Commercialization Commercialization
(South Korea) Hanwha Q Cells, S-Energy (Overseas) Trina, JA Solar, Ginko (China), Sharp, Kyocera,
Mitsubishi Electric (Japan)
Thin-film
Amorphous or microcrystalline Si thin- film type deposited on a
wafer Advantage: large-scale, mass
production possibilities Challenge: low efficiency
~9%
(module) Commercialization
(South Korea) None (Overseas) Sharp, Kaneka, Fuji
Batteries (Japan), GS Solar (China), Next Power (Taiwan)
Compound based
CIGS
Thin-film type made of Cu, In, and Se Advantage: resource conservation, potential for mass
production, and potential for high-performance Challenge: unavailability
~16%
(module) Commercialization
(South Korea) CIGSone (Overseas) Solar Frontier (Japan), Harnergy (China),
Miasole (US)
CdTe
Thin-film type made of Cd and Te
Advantage: resource conservation, potential for mass
production and lower cost Challenge: Cd toxicity
~15%
(module) Commercialization (South Korea) None (Overseas) First Solar (US)
Concentrated photovoltaics
Application of light harvesting and III-V compound multi-
junction Advantage: ultra-high
performance Challenge: lower cost
~38%
(cell) Research phase
(South Korea) BJ Power, Any Casting, Peru (Overseas) Sharp (Japan), Amonix (US), Soitec (Germany)
Organic- based
Dye-sensitized
New type solar cell that generates power from the dye bonding to TiO2 to absorb light Advantage: potential for lower
cost Challenge: high efficiency,
durability
~12%
(cell) Research phase
(South Korea) DongjinSemichem, Sangbo,
Eagon (Overseas) Dyesol (Australia),
Fujikura (Japan)
Organic thin- film
Thin-film type using organic semiconductor Advantage: potential for lower
cost Challenge: high-efficiency,
durability
~12%
(cell) Research phase
(South Korea) Kolon, LG Chem (Overseas) Heliatek (Germany), Mitsubishi, Sumitomo, JX energy
(Japan)
Organic/
inorganic- Perovskite
New type solar cell that generates power using light-
absorbing properties of perovskite, an organic/inorganic
compound ~22%
(cell) Research phase
(South Korea) Korea Research Institute of Chemical Technology,
Ulsan National Institute of Science and Technology, Sungkyunkwan University
4.1.1.2.1 Crystalline Si Solar Cell
The Panasonic Company (post-merger with Sanyo) of Japan holds the world record for conversion efficiency of monocrystalline Si solar cells, 25.6% (143.7 cm2), set in 2014 by adopting a back-contact HIT solar-cell structure. As regards polycrystalline Si solar cells, Trina Solar in China set a new world record for conversion efficiency of 21.25% (156 mm × 156 mm) in 2015.
Currently, the back-surface-field p-type screen-printed cell accounts for more than 90% of the total global production of crystalline Si solar cells. The average efficiencies of monocrystalline (156 mm × 156 mm) and polycrystalline cells in production are 19.5~20% and 18%~19%, respectively.
The maximum theoretical efficiency of crystalline Si solar cells has been reached almost, which leaves little room for significant improvements in performance through research and development. Therefore, the focus of current research and development is on cost reduction through material development and manufacturing technology advancement rather than efficiency improvement. In addition, studies are being conducted on protective materials to increase battery life. Other current areas of research include reducing polysilicon consumption by decreasing the wafer thickness and searching for a solution to the decline in efficiency during the module production (cell-to-module [CTM] loss).
4.1.1.2.2 Thin-Film Solar Cell
Thanks to its low production cost and versatile applications, the thin-film solar cell is considered a promising candidate for the next-generation solar cell to replace the crystalline Si solar cell. The manufacturing process of thin-film solar cells is relatively simple and they can be manufactured with low- cost wafers, such as glass, instead of silicon wafer, which, in turn, reduces the manufacturing cost. Their light-weight and flexible properties are expected to contribute to the application of thin-film solar cells in a wide range of products, such as exterior cladding materials for buildings. Thin-film solar cells are classified into amorphous silicon, compound semiconductor (CIGS and CdTe), dye-sensitized (DSSC), organic (OPV), and perovskite solar cells. The compound semiconductor solar cells (CIGS and CdTe) and the amorphous Si solar cells are currently being mass produced. The CdTe and CIGS solar cells are expected to capture a higher market share in the future. The amorphous Si solar cells has dominated the early thin-film solar cell market, but delayed efforts to improve cost competitiveness and efficiency have gradually undermined their market position. However, amorphous Si solar-cell technology is being integrated into Si solar-cell technology because of its usefulness in improving the efficiency of crystalline silicon. Although CdTe solar cells currently has the largest market share of the thin-film solar cells, market expansion is expected to be limited because of the toxicity of Cd and the difficulties to procure raw material. The CIGS- type solar cells are expected to become a leading contributor to the thin-film solar cell market thanks to their
high efficiency and potential for low-cost production. However, challenges remain, such as that competitiveness must be ensured, particularly in the mass-production system to achieve breakthrough growth. Several companies have started to release various semi-mass-produced solar cells (dye-sensitized and organic solar cells) ahead of their commercialization. Generally, it is expected that the commercialization hurdles, such as low efficiency and stability, which have offset the benefits in terms of manufacturing cost and applicability, will be overcome to some extent. At the beginning of 2016, since the discovery of the organic-inorganic perovskite compound from doing research to solidify dyes for dye- sensitized solar-cells, a research institute in South Korea recorded the world-class level efficiency of 22.1%.
This raises the expectations about future high-efficiency and high-stability thin-film solar-cell technology.
Furthermore, the research on quantum dot solar cells is at the early stages. In pursuit of high photovoltaic conversion efficiency through the arrangement of different size particles, researchers attempt to take advantage of the phenomenon that smaller semiconductor particles can absorb light with shorter wavelengths and larger particles can absorb light with longer wavelengths.
4.1.2 Wind power
4.1.2.1 Overview
Wind power is a key RE source and the generation technology takes advantage of the kinetic energy in wind to produce electricity. Wind power is a clean energy source, i.e., GHG emissions are not produced, makes it a leading countermeasure against climate change.
[Figure 4-4] Working mechanism of wind turbine
Wind spins the blades of the turbines, which spins the main shaft, gearbox, and generator consecutively to generate electricity. In contrast to its simple operation principle, the key components of wind turbines require considerable high-technology input in terms of their design and manufacturing, and the system control. Since the first wind turbine was invented by Charles Brush, it has taken approximately 130 years to develop a modern, MW-class wind turbine. The blades of wind turbines function on the same principle as airplane wings, i.e., the lift force, which is generated by the wind passing over the blade surface, activates the blades. Most MW-class wind-turbine blades have a rotational speed of 15~25 rpm. Longer blades are used to improve efficiency in areas with lower average wind speeds. In accordance with the International Electrotechnical Commission (IEC) criteria, the blade length of Class I blades is typically approximately 50 m, even for a large-capacity (3 MW) wind turbine. The length of Class II blades, designed for lower wind speeds, is approximately 60 m.
As the generator cannot produce electricity at a low rotational speed, a gearbox is employed often in wind turbines to increase the rotational speed. The gearbox accelerates the rotational speed of the blades to drive the generator. Wind turbines are classified into two types, namely, gearbox driven and direct drive.
The desired rotational speed of wind turbines without a gearbox can be achieved by increasing the number of poles in the permanent magnet mounted on the generator.
[Figure 4-5] Trend toward larger-capacity wind turbines
Source: KEA (2016a), Renewable Energy White Paper
As shown in [Fig. 4-5], after the commercialization of 1~2 MW wind turbines in the early 2000s, it took five years for 5 MW wind turbines to be commercialized. In 2015, the Vestas V164 8 MW was the world’s largest wind turbine.
4.1.2.2 Global Trends in Technology Development
In Europe and the US, efforts are underway to advance various technologies intended to reduce the levelized cost of energy (LCOE). LCOE, a concept that includes depreciation and financing cost, such as project financing, is the total cost input from the initial stage in the planning of a wind farm to the demolition after the termination of its life cycle divided by the total energy output over the entire life cycle.
Turbine costs account for the largest percentage of the LCOE composition, followed by the balance of system (grid connection cost). Therefore, wind turbine manufacturers focus more on cost reduction, whereas wind farm developers and operators are committed usually to minimizing the grid connection costs.
[Figure 4-6] Composition of LCOE of onshore wind power
Source: KEA (2016a), Renewable Energy White Paper
[Figure 4-7] Composition of LCOE of offshore wind power
Onshore and offshore wind power have different LCOE compositions because offshore wind power requires additional equipment, such as substructures and submarine power cables, owing to the challenges associated with such installation. In addition, extra insurance premiums and reserve funds are required for offshore installations.
The European Union is pursuing technology development to reduce the current LCOE rate of 11~18 cent (EUR)/kWh to 9 cents (EUR)/kWh by 2020 for offshore wind power. Siemens, who has the largest market share in offshore wind power, aims to reduce the LCOE rate to a maximum of 5 cent (EUR)/kWh, much lower than the EU target. DONG Energy, one of the major developers of wind farms, remains committed to reducing LCOE by 20~30% by 2017.
The Nuclear Energy Agency (NEA) of the Organization for Economic Cooperation and Development (OECD) has recently analyzed the LCOE of 181 power plants in 22 member states that are scheduled to start their commercial service in 2020. The results showed that nuclear power generation is the lowest at 47.4 USD/MWh, followed by onshore wind (74.7 USD/MWh), coal-fired (76.3 USD/MWh), natural gas (98.3 USD/MWh), and solar PV (121.6 USD/MWh). This implies that grid parity, at which the unit cost of onshore wind-power generation becomes cheaper than coal-fired power generation, could be reached by 2020. Distribution difficulties and a relatively high unit cost compared with fossil fuels have previously impeded wind power generation; however, the unit cost has been dropping because of continuing technological advancements.
4.1.3 Hydropower
4.1.3.1 Overview
Hydropower converts the potential energy stored in water in rivers or lakes into mechanical rotational energy by using hydraulic turbines, which, in turn, converts the resulting energy into electric energy. The capacity of the generating unit is determined by the head (H) and the flow (Q). There are several types of hydropower, namely, storage hydropower that derives from the energy of falling water (head), run-of-river hydropower that blocks the upper river and creates an intake that channels the water from upstream through a penstock or canal to use the head of the mainstream for power generation, a hybrid of storage and run-of- river hydropower that combines the advantages of both to obtain higher head, and river diversion hydropower that diverts a river’s flow to increase the head.
[Figure 4-8] Schematic diagram of hydropower plant
As shown in [Fig. 4-8], the hydropower system consists of a penstock that channels the water from a dam or barrage built in a river or reservoir to the power plant, a turbine that converts potential and kinetic energy stored in a water body into mechanical rotational energy, a generator, transmission and a substation to distribute the electricity, and a surveillance and control unit for plant operation, such as power output control.
❙ Table 4-2 ❙ Life cycle GHG emissions from different power sources
Technology Description 50th percentile
(CO2/kWh)
Hydropower Reservoir 4
Wind power Onshore 12
Nuclear energy Various generation II reactor types 16
Biomass Various 18
Solar thermal Parabolic trough 22
Geothermal energy Hot dry rock 45
Solar PV Polycrystalline silicon 46
Source: KEA (2016a), Renewable Energy White Paper
According to the Intergovernmental Panel on Climate Change (IPCC) report, hydropower offers a significant contribution to global warming prevention. This is because it is clean energy, with relatively low carbon dioxide (CO2) emissions compared with other RE sources, such as geothermal and wind power, or fossil fuels, including petroleum and coal.
Hydropower can start to generate electricity within a short time, less than five minutes, and is able to respond quickly to changes in the demand of the power grid. This means that hydropower plays a key role in stabilizing the power grid through peak load and frequency control. Compared with other power sources, hydropower has relatively low production costs and a stable cost structure, in which capital cost accounts for the major proportion, with little inflation or fluctuations in fuel prices. Hydropower, by replacing heavy oil generator with high variable costs, can contribute to price stabilization in the electricity market at peak times.
❙ Table 4-3 ❙ Classification of small hydropower
Source: KEA, KNREC, http://www.knrec.or.kr/
Small hydropower uses the potential energy from heads of water retained in rivers or reservoirs to activate the turbine, which exerts a turning force, and finally produces electricity through a generator connected to the turbine. Small hydropower can be classified based on facility capacity, head, and power generation method.
Sorting remarks
Facility capacity
Micro hydropower Mini hydropower Small hydropower
Less than 100 kW 100~1,000 kW 1,000~10,000 kW
Types of small hydropower available in South Korea include low head, tunnel, and storage hydropower Head
Low head Medium head High head
2~20 m 20~150 m More than 150 m
Power generating
method
Run-of-river type Storage type Tunnel type
A site where the river makes an omega-shaped bend (Ω) Middle and upper stream areas with high gradient streams A site with low gradient streams and high flow
❙ Table 4-4 ❙ Types and characteristics of water turbine
water turbine Characteristics
Impulse turbine
Pelton turbine Turgo turbine Ossberger turbine
- turbine is not immersed fully in water - water is fed only in a certain direction of the
turbine, and only kinetic energy is converted
Reaction turbine
Francis turbine - turbine is immersed fully in water
Propeller turbine
Kaplan turbine Tubular turbine Bulb turbine Rim turbine
- water is fed in a radial direction of the turbine - dynamic pressure and static pressure are converted
Source: KEA, KNREC, http://www.knrec.or.kr/
4.1.3.2 Global Trends in Technology Development
After two oil crises in the 1970s, many developed countries began to invest heavily in the development of hydropower technology, and have standardized the water turbines by types, to be suitable for use in the reference range based on the heads and flows in the early 1990s. Mass production has enabled saving on the construction costs of water turbines, making hydropower more cost effective. Currently, strong government support is being provided for the exploitable resources.
❙ Table 4-5 ❙ Status of turbine manufacturers by country
Country Production Company Turb type
USA Allis-Chalmer Co Tube, Francis, Propeller Turbines
Japan Fuji Francis, Tube, Bulb Turbines
China CMEC Francis, Kaplan Turbines
Norway GE Energy Bulb, Francis, Kaplan, Pelton, Propeller, Mini or Small-Scale Turbines
Germany Voith Hydro Pelton, Francis, Kaplan
Sweden TURAB Francis, Kaplan and Axial, Bulb and Axial Turbines Austria GEPPER Pelton, Francis, Diagonal, Kaplan, Compact Turbines France Alstom Francis, Pelton, S Type & Pit Turbines